The subject invention relates to an improved method for die cutting a plastic or paper web. The invention is applicable in the formation of plastic or paper trays, pouches and such composite structures for containing food and hospital or medical products. A preferred method of cutting is the high speed continuous die cutting machinery commonly used in the paper industry. In a typical operation, a plastic or paper web is continuously conveyed in a horizontal direction where it passes between a rotary die cutter and an anvil or support member. At desired places on the web, the rotary cutter is activated such that it penetrates the web. In order to avoid damage to the anvil member, which is typically a rotatable roller member, the cutter is set such that the blade portion thereof does not penetrate the entire thickness of the web. Rather, the blade penetrates the web only to an intermediate portion thereof, with the remaining portion of the web, typically having a thickness on the order of 0.0001-0.005 inches, being broken or shattered by the impact of the cutter blade together with the shearing force effected by the horizontal motion of the web. It has been found that as a result of this cutting procedure, the edge of the web formed by the cutter blade is clean while the edge of the web formed by the shattering or shearing of the web is rough, and includes a plurality of hair-like paper or plastic slivers. When a package formed from the specific web is filled with a food or other consumable product, there is often a tendency of the hair-like plastic or paper slivers to detach from the web and become embedded in the consumable product. It will be appreciated that such an effect is highly undesirable. Where the web is made of a paper material, die cutting of the material may also form paper dust in addition to paper slivers. This is of critical concern especially where the die cut paper is to form, for example, a blood filter used in apparatus employed in a hospital operating room. Any slivers or dust could, of course, be potentially dangerous if present in a hospital product.
Accordingly, it is an object of the subject invention to provide an improved method of die cutting a plastic or paper web which employs standard automatic die cutting machinery in which the edges of the cut webs are smooth without any hair-like sliver members.
It is another object of the invention to provide an improved method of die cutting a plastic or paper sheet with any form of die cutting apparatus such as rotary, reciprocal or flat bed.
It is a further object of the subject invention to provide an improved method having the above characteristics which is simple yet efficient and reliable.